We deprecated an overflow property for dataview/listview/tabcontainers.
"Widgets that are able to scroll their content (e.g. data view and groups box) no longer define overflow if they should not show a scrollbar. Floating dom nodes that relied on the overflow of their parent to clear the float will have to clear their float explicitly."
Example: the class mx-dataview-content used to have overflow: auto but we removed that by default
What I think happens in your situation is that elements are being floated and do not get a proper clear (clear: both) and that's why the content "Falls" outside the box. If you would try to put a clear: both;
on a elements after elements that gets float it should be fixed.
Example by CSS tricks